555 Circuits


Posted on Feb 4, 2014

This is a simple yet effective darkness activator. It uses an LDR to detect the light and when no light is present, it will sound an alarm from a cheap 8Ohm speaker. This circuit can be easily converted to a light detector by simply adding an inverting transistor driver at the output of the 555. This circuit performs a power failure alarm. It is a


555 Circuits
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555 oscillator that is off due to the fact that voltage appears at pin 7. When the voltage at pin 7 fails to appear, the alarm will sound from the buzzer. This is a simple metronome circuit that is useful for the friends of music. It will generate the classic toc-toc sound like the mechanical metronomes. The period of the signs can be adjusted from the 250K potentiometer. generator, AKA Morse code generator. The circuit will generate the characteristic `beep` sound of the Morse code generators, every time the switch is pressed. The missing pulse detector is actually a one-shot device that is continuously re-triggered from the input pulse. The component values for the resistor and the capacitor are to be changed to fit your needs. You should select the parts so that the delay should be about 30-40% bigger than the period of the input pulses. If it is bigger than two input pulses, then in order to detect the input pulse, there must be at least two input pulses missing. This is a touch switch version of the 555 switch connected as monostable multivibrator. The 2N2222 shall perform an amplifier able to sense slight loads on the plate such as static electricity from the human body. A switch debouncer is a mid-stage block that will clear and square the signal from a push button or a switch. Those switches are very noisy and the output waveform is filled with noise that will generate false pulses, due to poor contact condition,...




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